The invention relates to a rotary drum or disc filter comprising a filter sheet material carried by a rotary structure which is partly submerged in a liquid to be filtered and provides a plurality of circumferentially distributed cells on the inner side of said filter sheet material.
In filters of this type, filter cake is blown off from the filter sheet material in a predetermined position of each cell, which position is located above the level of submersion. For this purpose each cell is connected through a pipe to a manifold where valve functions in various arrangements are provided for the supply of vacuum and pressure to the individual cells in the correct position. This alternate supply of vacuum and pressure to the cells through the same pipes requires valve constructions, frequently slide valves, which are expensive to produce and often require considerable monitoring and maintenance.